Dropping the gas tank would've been bad. What he did looks stupid, but if he'd dropped a full gas tank, you can see what would've happened with the pile of fire at the end after he dropped the mostly empty one.

Actualy, spinning like that was ingenious. By doing so, he kept the outflow of gasoline constant enough to prevent the flames to enter the consealed container, which would explode from the pressure increase of the gasoline turning into a gas form.